Viscous couplings or clutches are clutches that are provided with reciprocally interlocking disks that rotate on a common axis in a housing containing a viscous fluid that is in contact with the frictional surfaces. Such couplings or clutches are, for example, used in different pawls and in interaxial differential gears of land-based vehicles and are described, for example, in German Patent Application No. 21 35 791 (disclosed on February 1972, A.P.R. Rolt et al). When used as components of interaxial differential gears, viscous couplings enable the positive or negative transmission of power from the drive shaft on the other axle or axles. The amount of torque transmitted depends on the difference in the number of rotations between the wheels or pairs of wheels concerned. For example, it becomes possible to prevent the wheels of a vehicle from moving when the vehicle's engine is started. When the viscous coupling or clutch is engaged, the viscous fluid that comes in contact with the frictional surfaces is subjected to high shearing stresses which can cause the temperature of the fluid to exceed 250.degree. C. Heretofore, silicon oils were suitable for this purpose only to a limited extent.
Therefore, it is an object of the present invention to provide stabilized silicon oils. Another object of the present invention is to provide silicon oils whose viscosity does not decrease substantially, even when the temperature of these oils attains 250.degree. C. over an extended period of time. A further object of the present invention is to provide silicon oils which under the operating conditions of viscous couplings do not form gaseous products under those temperatures and pressures. A still further object of the present invention is to provide a method for preparing silicon oils that are stable under elevated temperatures and pressures.